Can I crossfire two different GPUs?

Can I crossfire a xfx 7770 1gddr5 and an Asus 7770 2gddr5 ? If so what else could I crossfire with the xfx 7770 that may be better?

You can crossfire any 7770 with any other 7770 or a 7750.

Since you're using a 7770, you should just get another 7770 because if you crossfire it with a 7750, the 7770 is only going to give you the performance of a 7750. As long as they're both 7770s, the manufacturer and amount of RAM doesn't matter.

For the price of a second 7770 + the selling price of your current 7770, you could grab something like a 7850. I don't really advocate crossfiring two low-end cards. Dual GPU configurations can lead to a lot of headaches!

The 7850 can play games on high/ultra at 1080p. You don't need much more than that, and they are pretty inexpensive. Only a little more than a 7770.